British Airways is seeking a high court injunction against a 12-day Christmas strike by cabin crew after claiming that the strike ballot was illegal.

A legal hearing is scheduled for 2pm tomorrow as BA attempts to prevent the strike going ahead between 22 December and 2 January and disrupting the travel plans of almost 1 million passengers. Willie Walsh,

BA chief executive, said: "We are absolutely determined to do whatever we can to protect our customers from this appalling, unjustified decision from Unite. We do not want to see a million Christmases ruined." Taking a hardline stance with the union, Walsh accused it of "cynically" proceeding with the action despite knowing that it might be blocked after being sent three letters warning that industrial action might be illegal. "It cynically went ahead with an extreme, highly publicised threat to our customers and our business in the knowledge that it might not be able to carry it out."

This morningThe joint general secretaries of Unite, Tony Woodley and Derek Simpson, said Walsh had turned down an offer to declare a "pause for peace" last week.

"Christmas travel on British Airways is being held hostage by a macho management which prefers imposition and confrontation, or even litigation, to negotiation," they said.

BA's legal arguments rests on the balloting of cabin crew who have accepted voluntary redundancy. About 1,000 cabin crew have accepted payoffs in recent months, but may have filled in ballot forms while they were awaiting BA's response to their redundancy applications.

A leading industrial relations lawyer warned that the injunction attempt would fail if Unite could prove that it made "reasonable" attempts to ensure that the ballots were valid. "If the union has accidentally given the right to vote to people who were on the cusp of redundancy then the union will have a good case," said Mark Meryon, industrial relations partner at the law firm Bircham Dyson Bell.

Tonight Unite representatives were attempting to delay the injunction hearing until Thursday because some witnesses were unavailable.

The development adds to the uncertainty for BA passengers who have booked flights during the strike period and are considering whether to reschedule, book with rival airlines or make their trip by train or car instead.

BA is attempting to salvage as much of its schedule as possible after the announcement of the lengthy walkout, amid union claims that a cabin crew strike will ground the carrier at all airports including Heathrow, Gatwick and Manchester.

BA said this afternoon that it was scouring staff rotas and flight schedules to examine whether some services could go ahead. "As a backup to the legal action, British Airways managers have been establishing which cabin crew might wish to work normally during the strike period," said BA.

The airline added that 50 daily services to and from City airport, east London, will not be affected because BA operates from there under a separate subsidiary.

According to one estimate of compensation being discussed among union members, BA could sue for damages of up to £1m per day if a legal ruling says that the strike vote was null and void. However, Unite is confident that an 80% turnout of members, with more than 90% voting in favour, is a strong enough mandate to push ahead with industrial action.

Unite officials are adamant that a walkout will ground the entire airline apart from a handful of long-haul services that are scheduled to arrive at Heathrow on 22 and 23 December.

A BA spokesman said: "We are looking at our contingency plans. It will involve a large amount of work and we will look at every option available to us."